I'm testing out some various compilation schemes with DMD. Right now I'm
spawning multiple threads which simply do a `system` call with a string like
"DMD -c somefile.d". I'd like to limit the number of active threads to
something my CPU can handle (4 in this case since I've got 4 cores..).
How do I go about doing this?
Here's the function which I spawn:
void compileObjfile(string name)
{
shell(r"dmd -od" ~ r".\cache\" ~ r" -c -version=Unicode
-version=WindowsNTonly -version=Windows2000 -version=WindowsXP -I..\ " ~ name ~
" ");
}
So I just need to pass the module name to it. The trouble is, if I spawn this
function inside a foreach loop, I'll inadvertently create a few dozen threads.
This hogs the system for a while. :) (although this does seem to create some
rather impressive compilation speeds, LOL!)
This is what the main function might look like:
void main()
{
foreach (string name; dirEntries(curdir, SpanMode.shallow))
{
if (name.isfile && name.getExt == "d")
{
spawn(&compileObjfile, name);
}
}
}
Sidenotes: So I've tried compiling the win32 libraries via `DMD -lib`. DMD eats
up over 300 Megs of memory, and its quite scary how fast that number grows. It
took over 25 seconds to compile a lib file.
On the other hand, compiling .obj files one by one by blocking a single thread
on system calls (in other words, single-threaded version), it takes about 15
seconds to create a library file. In each instantiation DMD wastes only about a
dozen or so Mbytes, maybe less.
When I spawn an unlimited number of threads via a foreach loop, again compiling
object-by-object, the lib file is generated in only 5(!) seconds. I'm running a
quad-core on XP32, btw.
So I'm a little perplexed, because according to Tomasz (maker of xfBuild) and
his various posts, compiling .obj by .obj file should apparently be really
really slow and -lib makes the fastest builds. But I'm getting the exact
opposite results.
